<?php

/*
 * This file is part of SwiftMailer.
 * (c) 2004-2009 Chris Corbyn
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

/**
 * Defines the grammar to use for validation, implements the RFC 2822 (and friends) ABNF grammar definitions.
 *
 * @package    Swift
 * @subpackage Mime
 * @author     Fabien Potencier
 * @author     Chris Corbyn
 */
class Swift_Mime_Grammar
{
	/**
	 * Special characters used in the syntax which need to be escaped.
	 *
	 * @var string[]
	 */
	private static $_specials = array();

	/**
	 * Tokens defined in RFC 2822 (and some related RFCs).
	 *
	 * @var string[]
	 */
	private static $_grammar = array();

	/**
	 * Initialize some RFC 2822 (and friends) ABNF grammar definitions.
	 */
	public function __construct()
	{
		$this->init();
	}

	public function __wakeup()
	{
		$this->init();
	}

	protected function init()
	{
		if (count(self::$_specials) > 0) {
			return;
		}

		self::$_specials = array(
			'(', ')', '<', '>', '[', ']',
			':', ';', '@', ',', '.', '"'
		);

		/*** Refer to RFC 2822 for ABNF grammar ***/

		// All basic building blocks
		self::$_grammar['NO-WS-CTL'] = '[\x01-\x08\x0B\x0C\x0E-\x19\x7F]';
		self::$_grammar['WSP'] = '[ \t]';
		self::$_grammar['CRLF'] = '(?:\r\n)';
		self::$_grammar['FWS'] = '(?:(?:' . self::$_grammar['WSP'] . '*' .
			self::$_grammar['CRLF'] . ')?' . self::$_grammar['WSP'] . ')';
		self::$_grammar['text'] = '[\x00-\x08\x0B\x0C\x0E-\x7F]';
		self::$_grammar['quoted-pair'] = '(?:\\\\' . self::$_grammar['text'] . ')';
		self::$_grammar['ctext'] = '(?:' . self::$_grammar['NO-WS-CTL'] .
			'|[\x21-\x27\x2A-\x5B\x5D-\x7E])';
		// Uses recursive PCRE (?1) -- could be a weak point??
		self::$_grammar['ccontent'] = '(?:' . self::$_grammar['ctext'] . '|' .
			self::$_grammar['quoted-pair'] . '|(?1))';
		self::$_grammar['comment'] = '(\((?:' . self::$_grammar['FWS'] . '|' .
			self::$_grammar['ccontent'] . ')*' . self::$_grammar['FWS'] . '?\))';
		self::$_grammar['CFWS'] = '(?:(?:' . self::$_grammar['FWS'] . '?' .
			self::$_grammar['comment'] . ')*(?:(?:' . self::$_grammar['FWS'] . '?' .
			self::$_grammar['comment'] . ')|' . self::$_grammar['FWS'] . '))';
		self::$_grammar['qtext'] = '(?:' . self::$_grammar['NO-WS-CTL'] .
			'|[\x21\x23-\x5B\x5D-\x7E])';
		self::$_grammar['qcontent'] = '(?:' . self::$_grammar['qtext'] . '|' .
			self::$_grammar['quoted-pair'] . ')';
		self::$_grammar['quoted-string'] = '(?:' . self::$_grammar['CFWS'] . '?"' .
			'(' . self::$_grammar['FWS'] . '?' . self::$_grammar['qcontent'] . ')*' .
			self::$_grammar['FWS'] . '?"' . self::$_grammar['CFWS'] . '?)';
		self::$_grammar['atext'] = '[a-zA-Z0-9!#\$%&\'\*\+\-\/=\?\^_`\{\}\|~]';
		self::$_grammar['atom'] = '(?:' . self::$_grammar['CFWS'] . '?' .
			self::$_grammar['atext'] . '+' . self::$_grammar['CFWS'] . '?)';
		self::$_grammar['dot-atom-text'] = '(?:' . self::$_grammar['atext'] . '+' .
			'(\.' . self::$_grammar['atext'] . '+)*)';
		self::$_grammar['dot-atom'] = '(?:' . self::$_grammar['CFWS'] . '?' .
			self::$_grammar['dot-atom-text'] . '+' . self::$_grammar['CFWS'] . '?)';
		self::$_grammar['word'] = '(?:' . self::$_grammar['atom'] . '|' .
			self::$_grammar['quoted-string'] . ')';
		self::$_grammar['phrase'] = '(?:' . self::$_grammar['word'] . '+?)';
		self::$_grammar['no-fold-quote'] = '(?:"(?:' . self::$_grammar['qtext'] .
			'|' . self::$_grammar['quoted-pair'] . ')*")';
		self::$_grammar['dtext'] = '(?:' . self::$_grammar['NO-WS-CTL'] .
			'|[\x21-\x5A\x5E-\x7E])';
		self::$_grammar['no-fold-literal'] = '(?:\[(?:' . self::$_grammar['dtext'] .
			'|' . self::$_grammar['quoted-pair'] . ')*\])';

		// Message IDs
		self::$_grammar['id-left'] = '(?:' . self::$_grammar['dot-atom-text'] . '|' .
			self::$_grammar['no-fold-quote'] . ')';
		self::$_grammar['id-right'] = '(?:' . self::$_grammar['dot-atom-text'] . '|' .
			self::$_grammar['no-fold-literal'] . ')';

		// Addresses, mailboxes and paths
		self::$_grammar['local-part'] = '(?:' . self::$_grammar['dot-atom'] . '|' .
			self::$_grammar['quoted-string'] . ')';
		self::$_grammar['dcontent'] = '(?:' . self::$_grammar['dtext'] . '|' .
			self::$_grammar['quoted-pair'] . ')';
		self::$_grammar['domain-literal'] = '(?:' . self::$_grammar['CFWS'] . '?\[(' .
			self::$_grammar['FWS'] . '?' . self::$_grammar['dcontent'] . ')*?' .
			self::$_grammar['FWS'] . '?\]' . self::$_grammar['CFWS'] . '?)';
		self::$_grammar['domain'] = '(?:' . self::$_grammar['dot-atom'] . '|' .
			self::$_grammar['domain-literal'] . ')';
		self::$_grammar['addr-spec'] = '(?:' . self::$_grammar['local-part'] . '@' .
			self::$_grammar['domain'] . ')';
	}

	/**
	 * Get the grammar defined for $name token.
	 *
	 * @param string $name exactly as written in the RFC
	 *
	 * @return string
	 */
	public function getDefinition($name)
	{
		if (array_key_exists($name, self::$_grammar)) {
			return self::$_grammar[$name];
		} else {
			throw new Swift_RfcComplianceException(
				"No such grammar '" . $name . "' defined."
			);
		}
	}

	/**
	 * Returns the tokens defined in RFC 2822 (and some related RFCs).
	 *
	 * @return array
	 */
	public function getGrammarDefinitions()
	{
		return self::$_grammar;
	}

	/**
	 * Returns the current special characters used in the syntax which need to be escaped.
	 *
	 * @return array
	 */
	public function getSpecials()
	{
		return self::$_specials;
	}

	/**
	 * Escape special characters in a string (convert to quoted-pairs).
	 *
	 * @param string $token
	 * @param string[] $include additional chars to escape
	 * @param string[] $exclude chars from escaping
	 *
	 * @return string
	 */
	public function escapeSpecials($token, $include = array(), $exclude = array())
	{
		foreach (array_merge(array('\\'), array_diff(self::$_specials, $exclude), $include) as $char) {
			$token = str_replace($char, '\\' . $char, $token);
		}

		return $token;
	}
}
